Quality analysis of friction stir welded butt joints by means of experiments and simulations

Friction Stir Welding (FSW) is a solid-state welding process introduced and developed in the last decades. In this process a rotating tool is pressed on the two parts to be welded (mainly two plates), driven into the material and then translated along the parts interface. Academic and industrial interest is focused on the characteristics of the joined part in terms of mechanical resistance and fatigue resistance which are heavily related to the process parameters. In fact, the stirring phenomenon and the friction acting between the shoulder of the pin and the sheets, greatly increase the part temperature so that the material significantly changes its structural characteristics due to softening effect: grain dimensions, local hardness, grain orientation. FEM simulation of the process can add very useful information in defining how the process parameters influence the joint behavior. In the last years several efforts were oriented to the numerical simulation of the process, in order to investigate thermo-mechanical aspects, stress and strain distributions, thermal flow, residual stresses. The present paper deals with the set up of a FE model for the simulation of the FSW process whose results are correlated with the experimental observations carried out when joining AA6060-T6 aluminum alloy plates 5 mm thick with a cylindrical tool with flat shoulder. The information obtained from the model helped in the understanding of the welding phenomena.© (2012) Trans Tech Publications.